TransEBM v. 1.0: description, tuning, and validation of a transient model of the Earth's energy balance in two dimensions

Abstract. Modeling the long-term transient evolution of climate remains a technical and scientific challenge. However, understanding improving modeling behavior system increases confidence in projected changes mid- to future. Energy balance models (EBMs) provide simplified computationally efficient descriptions long timescales allow large ensemble runs by parameterizing energy fluxes. In this way, they can be used pinpoint periods phenomena interest. Here, we present TransEBM, an extended version two-dimensional model Zhuang et al. (2017a). Transient CO2, solar insolation, orbital configuration, fixed ice coverage, land–sea distribution are implemented as effective radiative forcings at land surface. We show that is most sensitive CO2 distribution, but obliquity mask have significant influence on modeled temperatures well. tune TransEBM reproduce 1960–1989 CE global mean temperature Equator-to-pole seasonal gradients ERA-20CM reanalysis (Hersbach al., 2015). The resulting latitudinal distributions agree well with general circulation (GCM) HadCM3 for simulation past millennium (Bühler 2020). does not represent internal variability ocean–atmosphere system, non-deterministic elements nonlinearity introduced through restarts randomized forcing. As facilitates simulations, envisage its use exploratory studies stochastic forcing perturbed parameterizations, thus complementing comprehensive GCMs.